A conventional general guard cable for a road prevents a vehicle travelling the road from falling to the outside of the road by installing a plurality of supports at a gap of about 5 meters at the roadside and by horizontally installing wire ropes of several lines (3-5 lines) at a gap at the supports.
In this way, in a state in which the guard cable for a road is installed at the roadside, when a vehicle travelling the road collides with the guard cable while deviating from a lane, wire ropes of several lines do not distribute an impact load when the vehicle collides and thus a phenomenon occurs that the impact load is concentrated to only one or two wire ropes in which the vehicle collides.
When a vehicle collides, as an impact load is concentrated to only a wire rope of one or two lines, a problem occurs that only a corresponding wire rope does not endure an impact load when the vehicle collides and that the vehicle falls to the outside of the road while the wire rope is instantaneously loosely untied or that the vehicle is caught between loosely untying wire ropes.